Inhibiting grain growth in metal composites

ABSTRACT

A process for producing composite metal articles whereby a suitable grain size is obtained in the metal member having the lowest temperature of recrystallization suitable for mechanical deformation, and the article produced thereby.

United States Patent Jerrold M. Alyea Alton, I11.

Appl. No. 760,992

Sept. 19, 1968 Oct. 26, 1971 Olin Mathieson Chemical Corporation INHIBITING GRAIN GROWTH IN METAL COMPOSITES 6 Claims, No Drawings U.S. Cl 148/127, 29/1963, 75/157.5,148/34 Int. Cl C21d1/32, B32b 15/00 Field of Search 148/127, 34,12;75/157.5;29/196.3

References Cited UNITED STATES PATENTS 10/1940 Copson 148/34 X 11/1945 Keene et a1. 148/12 2,417,760 3/1947 Keene 148/127 3,158,470 11/1964 Burghoffet a1..... 75/135 3,234,014 2/1966 McLain et al.... 75/157.5 X 3,402,043 9/1968 Smith 75/157.5

Primary ExaminerL. Dewayne Rutledge Assistant Examiner-G. K. White Attorneys- Robert H. Bachman, Henry W. Cummings,

Richard S. Strickler, Donald R. Motsko and Thomas P. ODay ABSTRACT: A process for producing composite metal articles whereby a suitable grain size is obtained in the metal member having the lowest temperature of recrystallization suitable for mechanical deformation, and the article produced thereby.

INHIBITING GRAIN GROWTH IN METAL COMPOSITES The present invention relates to composite metal articles. In particular the present invention resides in a process for producing a composite metal article whereby annealing does not cause excessive grain growth in one or more of the members, and the article produced thereby.

Composite articles comprising dissimilar metal members are highly desirable commercially due to the fact that the beneficial characteristics of, for example, the core and the cladding materials,.may be obtained in one composite article. In a single alloy frequently many properties cannot be greatly modified by alloying or thermal treatments, for example, such properties as modulus of elasticity, color, density, and strength 'in combination with high thermal or electrical conductivity.

However, by forming composites, apparent properties of the cladding can be generated while retaining the bulk properties of the core material. In this manner one can often obtain greatly modified and highly desirable properties over the single alloy.

For example, an iron base alloy has the advantage of high strength and cold formability. By forming iron composites one can retain these desirable properties while generating properties of the cladding, such as wear resistance, color, oxidation,

conductivity, or tarnish resistance and fine finishing, i.e., surface quality.

points of the dissimilar metal members. Thereupon, an unsuitable surface for commercial applications may result during subsequent mechanical working such as drawing or other forming operations.

It is therefore a principal object of the present invention to provide a new and improved process for producing composite metal articles, and the article produced thereby.

It is a further object of the present invention to provide a process as aforesaid whereby the process is simple, expeditious, and convenient to use.

It is still a further object of the present invention to provide a process as aforesaid which overcomes the numerous limitations and disadvantages attendant upon the formation of conventional composite articles having dissimilar metal member.

In accordance with the present invention, it has now been found that the foregoing objects may be readily attained. The process of the present invention readily overcomes the disadvantages of the art and achieves a simple and convenient process for obtaining a highly useful composite metal article.

The process of the present invention comprises: (A) the providing of a cold worked integral metal composite wherein the lower softening point metal member is a brass containing from 5.0 to 35.0 percent zinc which contains a grain-growthinhibiting element and (B) annealing said composite.

Preferably but not necessarily, the aforementioned members of the composite should be bonded together in accordance with the method of U.S. Pat. No. 3,381,365 since it is difficult to produce a composite metal article having an iron base core due to the formation of both adherent and flaky oxides at moderate or elevated temperatures necessary for hot rolling. This oxide layer frequently tends to break open during hot rolling but still can and often does cause severe problems.

Briefly, the process described in the aforementioned application provides for heating the iron base core, said core of a thickness of less than 0.50 inch, to a temperature between 300-:l,350 F., rolling together said core and cladding at a speed of at least feet per minute in one pass at a reduction range between 35 to75 percent with said core and cladding coming together for the first time in the bite of the rolls, said cladding of a thickness less than 0.25 inch, and contacting the roll prior to contacting the iron base core. lt is necessary that the included angle between the core and the cladding members is in excess of 5 upon entering the roll, with the preferred angle in excess of l0. An angle in excess of 10? will insure that the cladding members in the core do not come together earlier than in the bite of the rolls.

Upon entering the rolls, the cladding and the rolls are traveling at different linear speeds where as upon exiting from the rolls they are going at the same speed due to reduction in the thickness of the composite. The difference in travelling speeds between the rolls and the cladding in combination with the precontacting of the cladding and the rolls generates shear strain and introduces shearing in the biteof the rolls. and the core-cladding interface. The shearing strain in this interface results in turbulent material flow thereby causing more intimate bonding by increasing the interfacial linear surface of the composite by at least 20 percent. It is further noted that the interfacial surface between the core and the cladding members is characterized by the absence of interatomic diffusion between the core and the cladding members.

Naturally, other methods of bonding cladding members to an iron base core or to any desired core may also be employed. Thus, limitations as to thickness of the core and the cladding members need not apply.

Typical iron base alloys which may be employed include but are not limited to the following: high-purity iron, alloys of the iron-carbon family, iron-manganese family, iron-nickel family, iron-chromium family, and the iron-nickel-chromium family, etc.

Cladding alloys are selected from the brasses containing a grain-growth-inhibiting element and from 5.0 to 35.0 percent zinc, balance essentially copper.

it is a surprising finding in the present invention that an integral metal composite article may be produced wherein the resultant grain size, after annealing, of the lower softening point brass alloy cladding is within a range suitable for subsequent mechanical processing due to the presence of a graingrowth inhibitor in the brass alloy cladding. Thus a composite may be produced of a suitable quality for economic use. For example, the ,tendency to orange peel upon various working operations is eliminated, thus insuring a high-quality surface pleasing in appearance.

The melting and casting of the brass alloy is not especially critical and may be performed according to conventional mill practice.

Various grain-growth-inhibitor elements may be employed in the present invention. Elements such as, for example, iron, cobalt, phosphorus, calcium and mixtures thereof are readily applicable, with the preferred range of iron from 0.4 to 3.0 percent; of cobalt from 0.1 to 1.5 percent; of phosphorus up to 0.1 percent; and ofcalcium up to 0.l percent.

Thus after forming the metal composite, the lower softening point brass alloy cladding will not exhibit detrimental grain growth when the composite is annealed at a temperature sufficiently high to cause recrystallization or softening in the metal member requiring the highest temperature range; i.e., a temperature somewhat higher than the temperature required for recrystallization of the brassalloy cladding.

The annealing temperature is generally from 575 C. to l,000 C.; the actual temperature being dependent upon the particular alloy composition employed as the core and as the cladding. The resultant grain size of the brass alloy members after annealing is generally in the range of 0.005 mm. to 0.025 mm. and usually less than 0.015 mm.

Naturally, the process of the present invention is readily applicable to metal composites comprising brass alloys and metals other than, or in combination with, the aforementioned iron base alloys.

in addition, the process of the present invention is applicable wherein a single brass alloy member is clad to a single member of any of the aforementioned metals commonly employed as a core material.

The present invention will be more readily apparent from a consideration of the following illustrative examples.

EXAMPLE] EXAMPLE II A 70-30 cartridge brass containing approximately 1.0 percent iron as a grain-growth inhibitor was bonded on both sides of 40955. The resultant composite was annealed at a temperature of approximately 750 C. for l hour. The resultant grain size in the modified 70-30 brass component was found to be approximately 0.0l3 mm. and the resultant grain size in the stainless steel component was found to range from a No. 8 to a N0. 9 grain.

EXAMPLE Ill An 80-20 brass containing approximately 0.5 percent iron as a grain-growth inhibitor was bonded on both sides of SAE l|0 steel. The resultant composite was annealed at a temperature of approximately 600 C. for 1 hour. The resultant grain size in the modified brass was found to be approximately 0.008 mm. The resultant grain size in the steel component was found to range from a No. 9 to a No. [0 grain.

This invention may be embodied in other forms or carried out in other ways without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered as in all respects illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and all changes which come within the meaning and range of equivalency are intended to be embraced therein.

What is claimed is:

l. A process for obtaining an integral composite metal article having a suitable grain size for mechanical deformation which comprises:

A. providing a cold worked integral composite metal article comprising a brass component containing from 5 to 35 percent zinc and a grain-growth-inhibiting element selected from the group consisting of iron. cobalt, phosphorus, calcium, and mixtures thereof, balance essentially copper, integrally bonded to a side of an iron base component, and

B. recrystallizing annealing said composite article at a temperature of 575 to 1,000 C. wherein the resultant grain size of said brass is 0.005 mm. to 0.025 mm.

2. A process according to claim 1 wherein said element is iron and is present in an amount from 0.4 to 3.0 percent.

3. A process according to claim I wherein said element is cobalt and is present in an amount from 0.l to 1.5 percent.

4. A process according to claim I wherein said element is phosphorus and is present in an amount up to 0.l percent.

5. A process according to claim 1 wherein said element is calcium and is present in an amount up to 0.1 percent.

6. A process according to claim 1 wherein said brass component is bonded to two opposing sides of said iron base component.

i '0 Q t 

2. A process according to claim 1 wherein said element is iron and is present in an amount from 0.4 to 3.0 percent.
 3. A process according to claim 1 wherein said element is cobalt and is present in an amount from 0.1 to 1.5 percent.
 4. A process according to claim 1 wherein said element is phosphorus and is present in an amount up to 0.1 percent.
 5. A process according to claim 1 wherein said element is calcium and is present in an amount up to 0.1 percent.
 6. A process according to claim 1 wherein said brass component is bonded to two opposing sides of said iron base component. 